Vulcanization of chloroprene polymers



lower temperatures and in a shorter time than is Patented Feb. 26,1946 iR 2,395,493,

VULCANIZATION F CHLOROPRENE 1 POLYMERS HenryPaul Miller, Akron, Ohio,assignor to The J B, F. GoodrichCompany, New York; N. Y.,::.

corporation of New York i i No Drawing. Application May 21 194 3,

Serial No. 487,965

I p 7 Claims. (o1. Zea-92.7) v This invention relates to thevulcanization or least two, and which may be either primary curing ofsynthetic rubber compositions embody- (NH2--), secondary ing plasticrubbery polymers of halogen-substi- H r tuted butadienes-LB such asplastic polymerized j y (-N) 1. chloroprene (2-chloro-butadiene-L3),and, has as 5 or tertiary its principal object to provide a new class ofvul- -i]i-) canizing agents by the use of which such synthetic rubbercompositions may be cured efficiently and amine groups; the said, aminegroups bein teconomically to yield vulcanized products of imtached tocarbon atoms present in. alkylene proved quality; A groups, that is,bivalent open-chain aliphatic The vulcanization of plastic polymerizedchlorogroups having the two free valences attached to prene (hereinaftersometimes referred to as neodifferent carbon atoms. Theterm aliphaticpolyprene, the commercial name for this type of synamine as used hereinwill be understood to have thetic rubber) is ordinarily accomplishedbyheatthe foregoing meaning. Anyhydroxy substituted ingacompositioncontaining the synthetic rubber polyamine, i. e., an aliphaticpolyamine/having in admixture with metallic oxides such as zinc one ormore hydroxyl groups attached to carbon oxide and magnesium oxide andwith wood rosin' atoms, may also be employed.

or pine tar, to a temperature of about 160 to 320 The preferredcompounds of the classconsisting F. for about 30 to 120 minutes,whereupon the of aliphatic polyamines and 'hydroxy substituted plasticcomposition is converted into an elastic 2o aliphatic polyamines for useas vulcanizing agents vulcanized state. The presence of sulfur Or a,sulin this invention are the alkylene polyamines infur-liberatingcompoundis not essential for this .cluding the alkylene diamines such aethylene vulcanization, as it is the case of natural rubdiamine(1,2-diaminoethane), 1,2-diamino. probar, but sulfur may be present toaccelerate the pane, 1,3+diamin0 propane, 1,2,3 triaminoprovulcanizgtion, pane, 1,4-diamino butane, hexamethylene dia- Whilethis method of vulcanizlng neoprene has mine, l,10-diamino decane andthelike and the been more or less satisfactory, there are manyinpolyalkylene polyamines such as diethylene tristances, particularlywhen the material to be vulmin tri hylene tetramine, tetraethylene pcanized is a liquid composition such as a neoprene tamine, pentaethylenehexamine, dipropylene tricement, where it is desirable to effect a cureat amine, tetrabutylene pentamine, triamino triethyl amines, and thelike; the hydrocarbon substituted possible with this known vulcanizingtechnique. alkylene polyamines including amines :in which For exampleQithas not been possible to air cure the hydrocarbon group is attachedeither to a neoprene cements at room temperature in a few nitrogen or toan aliphatic carbon atom such as hours except by the further addition ofsulfur and dibutyl ethylene diamine, phenyl triethylene tetexpensivevulcanization accelerators to the comramine, triethyl diethylenetriamine, 2-amino triposition, which additions possess the disadvantageethylamine, 1,2-di(ethyl amino) ethane, 1,2di-

of undesirabl staining the final vulcanized com- (dimethyl amino)ethane, 1,3-di(methy1 amino) position. propane and the like; and thehydroxy substituted Ihave now discovered that plastic polymerizedalkylene polyamines in which the hydrox group halogen-substitutedbutadienes-1,3 may be rapidly is attached to an aliphatic carbon atomsuch as cured at low temperatures to produce non-stain- 1,2-diaminoethanol, 1,3-di(diethyl amino)proing vulcanizates by the use of one ormore mempanol, 1,3-diamino propanol and the like. The

bers of the class consisting of aliphatic polyamines polyalkylenepolyamines such as tetraethylene and hydroxy-substituted aliphaticpolyamines as pentamine are particularly preferred. All these thevulcanizingagents. Such amines may be inaliphatic polyamines andhydroxy-substituted alicorporated in solid or liquid compositionscomphatic polyamines may be represented by the prising such plasticrubbery polymers, which comstructural formula V positions may or may notcontain the usual vul- R X g canizing agents such as rosin and metallicoxides, 6

and the compositions then vulcanized. They may I i be added to neoprenesolutions and'cements to i R R produce compositions which will air curein a few wherein R is hydrogen, a hydrocarbon group or a, hours at roomtemperature and they may otherhydroxy or amino substituted hydrocarbongroup wise be used to replace or to supplement the con- X is hydrogen,hydroxy, a hydrocarbon group or a ventional vulcanizing agentsforneoprene. hydroxy or amino-substituted hydrocarbon group Thealiphatic polyamine employed may be any and n is an integer preferablygreater than 1. open-chained organiccompound consisting of car- In thepractice of the invention one or more of bon, hydrogen and nitrogen inwhich the nitrogen the above-mentioned polyamines is associated, ispresent in amine groups,of which thereare at with a plastic polymerizedchloropreneicomposition and thecomposltion is then vulcanized. Thepolyamine vulcanizing agents may be incorporated in neoprenecompositions while the synthetic rubber is being worked on a roll-millor masticated in an internal mixer, and they may be added alone or inadmixture with each other or.

with other compounding ingredients such as pigments, antioxidants,softeners, or other ingredients commonly used in compounding neoprene orin the form of a masterbatch. When the neoprene composition is in theform of a cement or dispersed in water or a solvent, the vulcanizingagents may be simply dissolved or dispersed therein. The vulcanizationof the neoprene composition containing the vulcanizing agent may beeffected in a heated mold, in open steam, in hot air or, in the eventthe composition is a solution or cement, simply by allowing thecomposition to stand at room temperature. The conditions required forvulcanization such as time and temperature will obviously be dependenton the nature of the particular composition to be vulcanized, and arenot critical.

The proportions of the polyamine vulcanizin agent to, be used may bevaried within wide limits. The use of from 0.5 to by weight of thepolyamine based on the neoprene is ordinarily sufficient and ispreferred, although greater or .smaller amounts may desirably beemployed in some cases.

cific example is set forth:

- for 3 hours at 158 F.

Example I l A rapid air curing neoprene cement useful in coatingfabrics, as an adhesive for binding various articles such as fabric,rubbery and plastic materials, leather etc. to each other, and for anyother suitable purpose is preparedfrom a neoprene composition containingthe following ingredients:

. Parts Neoprene G (a plastic polymerized chloroprene) 100 Magnesiumoxide 4 Zinc oxi 5 Litharge '5 Phenyl beta naphthylamine 2 Gastex carbonblack; 5

stand at room temperature for only 24 hours whereupon it is found thatthe neoprene coating is well-vulcanized and tightly adhered to thefabric. The film is clear, free from stain and is strong and elastic.When the cement is applied to an adhesive joint'of a composite structureand allowed to air curefor'24 hours at room temperature, strong,adhesive bonds are obtained. The cement may also be vulcanized in only 1hr. if heated to 158 F'. or in an even shorter time if heated to highertemperatures. When the allphatic polyamine is not present in the cement,howevenit is insufficiently cured even after days at room temperature orafter being heated Similar ultra-rapid air curing neoprene cements maybe prepared when ethylene diamine, dlethylene triamine, diaminopropanol, dibutyl ethylene diamine and similar aliphatic polyamines andhydroxy substituted aliphatic polyamines are substituted for thetetraethylene pentamine of the above example. Moreover such cements areobtained by the use of other neoprene compositionscontaining otheringredients than those present in the neoprene composition of the aboveexample, or even when the neoprene contains no added ingredients savethe aliphatic polyamine. Thus the presence of magnesium oxide and zincoxide in the neoprene composition is by no means essential and may besubstituted by other ingredients or omitted entirely if desired.Litharge may also be omitted but this is not preferred since it has beenfound that litharge is a particularly valuable accelerator for the vul-.canization with aliphatic polyamines.

In the preparation of such air curing cements it is also obviouslypossible to employ any volatile solvent for the neoprene composition inplace of the mixture of gasoline and isopropyl acetate. For example,benzene; toluene, ethylene dichloride, chlorobenzene, carbon disulfide,trichloroethylene, methyl ethyl ketone or the like or mixtures of thesemay be-usedto dissolve the neoprene composition.

The aliphatic polyamine is preferably added either alone or in solutionin'a solvent to a solutionof a neoprene composition, as in the aboveexample, to produce the air-curing cement. Since the polyamine rapidlysets-up or curesthe cement greatly increasing its viscosity, it isordinarily desired toadd the polyamineonly a short time before thecement is'tobe used. If the polyamine is addedto the cement before it isused and it is desired to prevent gelling and maintain as low aviscosity as possible it is advantageous to include in the cement amaterial which prevents or retards gelling such as ethyl'alcohol,glycerine or other aliphatic alcohols, phenols, organic acids, ormonoamines such asdiethyl amine or monoethanol amine.

. Example II The following ingredients are mixed on a tworoll mixingroll:

- Parts Neoprene G (a plastic polymerized chloro-- I prene) I 100 Phenylbeta-naphthylamine 2 Carbon black Paraffin oil 5 Thio beta naphthol 0.5Laurie. acid 2 Tetraethylenepentamine a 1 The resulting composition isthen vulcanized in a press for 20 minutes at 287 F. An excellentvulcanizate having high tensile strength and elongation is obtained. Itis to be noted that none of the conventional curing agents forneoprenesuch as metallic oxides and rosin is present in as butadiene-1,3,isoprene, acrylonitrile, styrene and the like. It is also within thescope of the invention to employ polyamines as vulcanizing agents formixtures of neoprene or other plastic polymers of a halogen-substitutedbutadiene-IB with other plastic rubbery vulcanizable materials such asnatural rubber and synthetic rubbers of the type prepared by thepolymerization of butadiene-l,3 either alone or in admixture withacrylonitrile, styrene, isobutylene, methyl methacrylate, etc. Asillustrated herein the materials to be vulcanized may be mixed with anyof the con ventional compounding ingredients such as antioxidants,fillers, pigments, softeners, plasticizers and the like.

Other modifications and variations of the invention will be apparent tothose skilled in the art and are within the spirit and scope oi. theinvention as defined by the appended claims.

1. The method which comprises vulcanizing plastic polymerizedchloroprene in the presence of a polyalkylene polyamine in which thealkylene roups are composed exclusively of carbon and hydrogen. i

2. The method which comprises vulcanizing plastic polymerizedchloroprene inthe presence of tetraethylene pentamine.

3. The method which comprises vulcanizing a plastic polymer consistingpredominantly of a polymerized halogen-substituted butadiene-1,3 in

the presence of a polyalkylene polyamine in which the alkylene groupsare composed exclusively of carbon and hydrogen.

4. An air curing synthetic rubber cement comprising, plastic polymerizedchloroprene, a volatile organic solvent therefor and polyalkylenepolyamine in which the alkylene groups are composed exclusively ofcarbon and hydrogen.

5. A composition of matter comprising a plastic polymer consistingpredominantly of a polymerized halogen-substituted butadiene- 1,3 and,as a vulcanizing agent therefor, a polyalkylene polyamine in which thealkylene groups are composed exclusively of carbon and hydrogen.

6. A vulcanizate prepared by the method of claim 1.

7. A vulcanizate prepared by the method of claim 3.

HENRY PAUL MILLER.

